linamh/app-emulation/kvm/files/kvm-preXX-init-on-demand.patch

From 3be490091c2503d8b50f4a0ce1efe68004f65d3e Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Tue, 4 Nov 2008 18:48:21 +0100
Subject: [PATCH] Activate Virtualization On Demand v3

X86 CPUs need to have some magic happening to enable the virtualization
extensions on them. This magic can result in unpleasant results for
users, like blocking other VMMs from working (vmx) or using invalid TLB
entries (svm).

Currently KVM activates virtualization when the respective kernel module
is loaded. This blocks us from autoloading KVM modules without breaking
other VMMs.

To circumvent this problem at least a bit, this patch introduces on
demand activation of virtualization. This means, that instead
virtualization is enabled on creation of the first virtual machine
and disabled on removal of the last one.

So using this, KVM can be easily autoloaded, while keeping other
hypervisors usable.

v2 adds returns to non-x86 hardware_enables and adds IA64 change
v3 changes:
  - use spin_lock instead of atomics
  - put locking to new functions hardware_{en,dis}able_all that get called
    on VM creation/destruction
  - remove usage counter checks where not necessary
  - return -EINVAL for IA64 slot < 0 case

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 arch/ia64/kvm/kvm-ia64.c   |    8 +++--
 arch/powerpc/kvm/powerpc.c |    3 +-
 arch/s390/kvm/kvm-s390.c   |    3 +-
 kernel/x86/svm.c         |   13 +++++--
 kernel/x86/vmx.c         |    7 +++-
 kernel/x86/x86.c         |    4 +-
 kernel/include/asm-x86/kvm_host.h |    2 +-
 kernel/include/linux/kvm_host.h   |    2 +-
 virt/kvm/kvm_main.c        |   75 ++++++++++++++++++++++++++++++++++++-------
 9 files changed, 90 insertions(+), 27 deletions(-)

Index: kvm-78/kernel/ia64/kvm-ia64.c
===================================================================
--- kvm-78.orig/kernel/ia64/kvm-ia64.c
+++ kvm-78/kernel/ia64/kvm-ia64.c
@@ -138,7 +138,7 @@ long ia64_pal_vp_create(u64 *vpd, u64 *h
 
 static  DEFINE_SPINLOCK(vp_lock);
 
-void kvm_arch_hardware_enable(void *garbage)
+int kvm_arch_hardware_enable(void *garbage)
 {
 	long  status;
 	long  tmp_base;
@@ -152,7 +152,7 @@ void kvm_arch_hardware_enable(void *garb
 	slot = ia64_itr_entry(0x3, KVM_VMM_BASE, pte, KVM_VMM_SHIFT);
 	local_irq_restore(saved_psr);
 	if (slot < 0)
-		return;
+		return -EINVAL;
 
 	spin_lock(&vp_lock);
 	status = ia64_pal_vp_init_env(kvm_vsa_base ?
@@ -160,7 +160,7 @@ void kvm_arch_hardware_enable(void *garb
 			__pa(kvm_vm_buffer), KVM_VM_BUFFER_BASE, &tmp_base);
 	if (status != 0) {
 		printk(KERN_WARNING"kvm: Failed to Enable VT Support!!!!\n");
-		return ;
+		return -EINVAL;
 	}
 
 	if (!kvm_vsa_base) {
@@ -169,6 +169,8 @@ void kvm_arch_hardware_enable(void *garb
 	}
 	spin_unlock(&vp_lock);
 	ia64_ptr_entry(0x3, slot);
+
+	return 0;
 }
 
 void kvm_arch_hardware_disable(void *garbage)
Index: kvm-78/kernel/x86/svm.c
===================================================================
--- kvm-78.orig/kernel/x86/svm.c
+++ kvm-78/kernel/x86/svm.c
@@ -300,7 +300,7 @@ static void svm_hardware_disable(void *g
 	wrmsrl(MSR_EFER, efer & ~MSR_EFER_SVME_MASK);
 }
 
-static void svm_hardware_enable(void *garbage)
+static int svm_hardware_enable(void *garbage)
 {
 
 	struct svm_cpu_data *svm_data;
@@ -309,16 +309,20 @@ static void svm_hardware_enable(void *ga
 	struct kvm_desc_struct *gdt;
 	int me = raw_smp_processor_id();
 
+	rdmsrl(MSR_EFER, efer);
+	if (efer & MSR_EFER_SVME_MASK)
+		return -EBUSY;
+
 	if (!has_svm()) {
 		printk(KERN_ERR "svm_cpu_init: err EOPNOTSUPP on %d\n", me);
-		return;
+		return -EINVAL;
 	}
 	svm_data = per_cpu(svm_data, me);
 
 	if (!svm_data) {
 		printk(KERN_ERR "svm_cpu_init: svm_data is NULL on %d\n",
 		       me);
-		return;
+		return -EINVAL;
 	}
 
 	svm_data->asid_generation = 1;
@@ -329,11 +333,12 @@ static void svm_hardware_enable(void *ga
 	gdt = (struct kvm_desc_struct *)gdt_descr.address;
 	svm_data->tss_desc = (struct kvm_ldttss_desc *)(gdt + GDT_ENTRY_TSS);
 
-	rdmsrl(MSR_EFER, efer);
 	wrmsrl(MSR_EFER, efer | MSR_EFER_SVME_MASK);
 
 	wrmsrl(MSR_VM_HSAVE_PA,
 	       page_to_pfn(svm_data->save_area) << PAGE_SHIFT);
+
+	return 0;
 }
 
 static void svm_cpu_uninit(int cpu)
Index: kvm-78/kernel/x86/vmx.c
===================================================================
--- kvm-78.orig/kernel/x86/vmx.c
+++ kvm-78/kernel/x86/vmx.c
@@ -1090,12 +1090,15 @@ static __init int vmx_disabled_by_bios(v
 	/* locked but not enabled */
 }
 
-static void hardware_enable(void *garbage)
+static int hardware_enable(void *garbage)
 {
 	int cpu = raw_smp_processor_id();
 	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
 	u64 old;
 
+	if (read_cr4() & X86_CR4_VMXE)
+		return -EBUSY;
+
 	INIT_LIST_HEAD(&per_cpu(vcpus_on_cpu, cpu));
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
 	if ((old & (FEATURE_CONTROL_LOCKED |
@@ -1110,6 +1113,8 @@ static void hardware_enable(void *garbag
 	asm volatile (ASM_VMX_VMXON_RAX
 		      : : "a"(&phys_addr), "m"(phys_addr)
 		      : "memory", "cc");
+
+	return 0;
 }
 
 static void vmclear_local_vcpus(void)
Index: kvm-78/kernel/x86/x86.c
===================================================================
--- kvm-78.orig/kernel/x86/x86.c
+++ kvm-78/kernel/x86/x86.c
@@ -4077,9 +4077,9 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu
 	return kvm_x86_ops->vcpu_reset(vcpu);
 }
 
-void kvm_arch_hardware_enable(void *garbage)
+int kvm_arch_hardware_enable(void *garbage)
 {
-	kvm_x86_ops->hardware_enable(garbage);
+	return kvm_x86_ops->hardware_enable(garbage);
 }
 
 void kvm_arch_hardware_disable(void *garbage)
Index: kvm-78/kernel/include/asm-x86/kvm_host.h
===================================================================
--- kvm-78.orig/kernel/include/asm-x86/kvm_host.h
+++ kvm-78/kernel/include/asm-x86/kvm_host.h
@@ -453,7 +453,7 @@ struct descriptor_table {
 struct kvm_x86_ops {
 	int (*cpu_has_kvm_support)(void);          /* __init */
 	int (*disabled_by_bios)(void);             /* __init */
-	void (*hardware_enable)(void *dummy);      /* __init */
+	int (*hardware_enable)(void *dummy);       /* __init */
 	void (*hardware_disable)(void *dummy);
 	void (*check_processor_compatibility)(void *rtn);
 	int (*hardware_setup)(void);               /* __init */
Index: kvm-78/kernel/include/linux/kvm_host.h
===================================================================
--- kvm-78.orig/kernel/include/linux/kvm_host.h
+++ kvm-78/kernel/include/linux/kvm_host.h
@@ -300,7 +300,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu);
 
 int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu);
-void kvm_arch_hardware_enable(void *garbage);
+int kvm_arch_hardware_enable(void *garbage);
 void kvm_arch_hardware_disable(void *garbage);
 int kvm_arch_hardware_setup(void);
 void kvm_arch_hardware_unsetup(void);
Index: kvm-78/kernel/x86/kvm_main.c
===================================================================
--- kvm-78.orig/kernel/x86/kvm_main.c
+++ kvm-78/kernel/x86/kvm_main.c
@@ -93,6 +93,8 @@ DEFINE_SPINLOCK(kvm_lock);
 LIST_HEAD(vm_list);
 
 static cpumask_t cpus_hardware_enabled;
+static int kvm_usage_count = 0;
+static DEFINE_SPINLOCK(kvm_usage_lock);
 
 struct kmem_cache *kvm_vcpu_cache;
 EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
@@ -103,6 +105,8 @@ struct dentry *kvm_debugfs_dir;
 
 static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
 			   unsigned long arg);
+static int hardware_enable_all(void);
+static void hardware_disable_all(void);
 
 bool kvm_rebooting;
 
@@ -592,19 +596,25 @@ static const struct mmu_notifier_ops kvm
 
 static struct kvm *kvm_create_vm(void)
 {
+	int r = 0;
 	struct kvm *kvm = kvm_arch_create_vm();
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	struct page *page;
 #endif
 
 	if (IS_ERR(kvm))
-		goto out;
+		return kvm;
+
+	r = hardware_enable_all();
+	if (r) {
+		goto out_err;
+	}
 
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (!page) {
-		kfree(kvm);
-		return ERR_PTR(-ENOMEM);
+		r = -ENOMEM;
+		goto out_err;
 	}
 	kvm->coalesced_mmio_ring =
 			(struct kvm_coalesced_mmio_ring *)page_address(page);
@@ -612,15 +622,13 @@ static struct kvm *kvm_create_vm(void)
 
 #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
 	{
-		int err;
 		kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
-		err = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
-		if (err) {
+		r = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
+		if (r) {
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 			put_page(page);
 #endif
-			kfree(kvm);
-			return ERR_PTR(err);
+			goto out_err;
 		}
 	}
 #endif
@@ -639,8 +647,12 @@ mmget(&kvm->mm->mm_count);
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	kvm_coalesced_mmio_init(kvm);
 #endif
-out:
 	return kvm;
+
+out_err:
+	hardware_disable_all();
+	kfree(kvm);
+	return ERR_PTR(r);
 }
 
 /*
@@ -689,6 +701,7 @@ static void kvm_destroy_vm(struct kvm *k
 	mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
 #endif
 	kvm_arch_destroy_vm(kvm);
+	hardware_disable_all();
 	mmdrop(mm);
 }
 
@@ -1796,14 +1809,40 @@ static struct miscdevice kvm_dev = {
 	&kvm_chardev_ops,
 };
 
-static void hardware_enable(void *junk)
+static void hardware_enable(void *_r)
 {
 	int cpu = raw_smp_processor_id();
+	int r;
+
+	/* If enabling a previous CPU failed already, let's not continue */
+	if (_r && *((int*)_r))
+		return;
 
 	if (cpu_isset(cpu, cpus_hardware_enabled))
 		return;
+	r = kvm_arch_hardware_enable(NULL);
+	if (_r)
+		*((int*)_r) = r;
+	if (r) {
+		printk(KERN_INFO "kvm: enabling virtualization on "
+				 "CPU%d failed\n", cpu);
+		return;
+	}
+
 	cpu_set(cpu, cpus_hardware_enabled);
-	kvm_arch_hardware_enable(NULL);
+}
+
+static int hardware_enable_all(void)
+{
+	int r = 0;
+
+	spin_lock(&kvm_usage_lock);
+	kvm_usage_count++;
+	if (kvm_usage_count == 1)
+		kvm_on_each_cpu(hardware_enable, &r, 1);
+	spin_unlock(&kvm_usage_lock);
+
+	return r;
 }
 
 static void hardware_disable(void *junk)
@@ -1816,6 +1855,18 @@ static void hardware_disable(void *junk)
 	kvm_arch_hardware_disable(NULL);
 }
 
+static void hardware_disable_all(void)
+{
+	if (!kvm_usage_count)
+		return;
+
+	spin_lock(&kvm_usage_lock);
+	kvm_usage_count--;
+	if (!kvm_usage_count)
+		kvm_on_each_cpu(hardware_disable, NULL, 1);
+	spin_unlock(&kvm_usage_lock);
+}
+
 static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
 			   void *v)
 {
@@ -2061,7 +2112,6 @@ int kvm_init(void *opaque, unsigned int
 			goto out_free_1;
 	}
 
-	kvm_on_each_cpu(hardware_enable, NULL, 1);
 	r = register_cpu_notifier(&kvm_cpu_notifier);
 	if (r)
 		goto out_free_2;
@@ -2114,7 +2164,6 @@ out_free_3:
 	unregister_reboot_notifier(&kvm_reboot_notifier);
 	unregister_cpu_notifier(&kvm_cpu_notifier);
 out_free_2:
-	kvm_on_each_cpu(hardware_disable, NULL, 1);
 out_free_1:
 	kvm_arch_hardware_unsetup();
 out_free_0:
Index: kvm-78/kernel/ia64/kvm_main.c
===================================================================
--- kvm-78.orig/kernel/ia64/kvm_main.c
+++ kvm-78/kernel/ia64/kvm_main.c
@@ -93,6 +93,8 @@ DEFINE_SPINLOCK(kvm_lock);
 LIST_HEAD(vm_list);
 
 static cpumask_t cpus_hardware_enabled;
+static int kvm_usage_count = 0;
+static DEFINE_SPINLOCK(kvm_usage_lock);
 
 struct kmem_cache *kvm_vcpu_cache;
 EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
@@ -103,6 +105,8 @@ struct dentry *kvm_debugfs_dir;
 
 static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
 			   unsigned long arg);
+static int hardware_enable_all(void);
+static void hardware_disable_all(void);
 
 bool kvm_rebooting;
 
@@ -592,19 +596,25 @@ static const struct mmu_notifier_ops kvm
 
 static struct kvm *kvm_create_vm(void)
 {
+	int r = 0;
 	struct kvm *kvm = kvm_arch_create_vm();
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	struct page *page;
 #endif
 
 	if (IS_ERR(kvm))
-		goto out;
+		return kvm;
+
+	r = hardware_enable_all();
+	if (r) {
+		goto out_err;
+	}
 
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (!page) {
-		kfree(kvm);
-		return ERR_PTR(-ENOMEM);
+		r = -ENOMEM;
+		goto out_err;
 	}
 	kvm->coalesced_mmio_ring =
 			(struct kvm_coalesced_mmio_ring *)page_address(page);
@@ -612,15 +622,13 @@ static struct kvm *kvm_create_vm(void)
 
 #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
 	{
-		int err;
 		kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
-		err = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
-		if (err) {
+		r = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
+		if (r) {
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 			put_page(page);
 #endif
-			kfree(kvm);
-			return ERR_PTR(err);
+			goto out_err;
 		}
 	}
 #endif
@@ -639,8 +647,12 @@ static struct kvm *kvm_create_vm(void)
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	kvm_coalesced_mmio_init(kvm);
 #endif
-out:
 	return kvm;
+
+out_err:
+	hardware_disable_all();
+	kfree(kvm);
+	return ERR_PTR(r);
 }
 
 /*
@@ -689,6 +701,7 @@ static void kvm_destroy_vm(struct kvm *k
 	mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
 #endif
 	kvm_arch_destroy_vm(kvm);
+	hardware_disable_all();
 	mmdrop(mm);
 }
 
@@ -1796,14 +1809,40 @@ static struct miscdevice kvm_dev = {
 	&kvm_chardev_ops,
 };
 
-static void hardware_enable(void *junk)
+static void hardware_enable(void *_r)
 {
 	int cpu = raw_smp_processor_id();
+	int r;
+
+	/* If enabling a previous CPU failed already, let's not continue */
+	if (_r && *((int*)_r))
+		return;
 
 	if (cpu_isset(cpu, cpus_hardware_enabled))
 		return;
+	r = kvm_arch_hardware_enable(NULL);
+	if (_r)
+		*((int*)_r) = r;
+	if (r) {
+		printk(KERN_INFO "kvm: enabling virtualization on "
+				 "CPU%d failed\n", cpu);
+		return;
+	}
+
 	cpu_set(cpu, cpus_hardware_enabled);
-	kvm_arch_hardware_enable(NULL);
+}
+
+static int hardware_enable_all(void)
+{
+	int r = 0;
+
+	spin_lock(&kvm_usage_lock);
+	kvm_usage_count++;
+	if (kvm_usage_count == 1)
+		on_each_cpu(hardware_enable, &r, 1);
+	spin_unlock(&kvm_usage_lock);
+
+	return r;
 }
 
 static void hardware_disable(void *junk)
@@ -1816,6 +1855,18 @@ static void hardware_disable(void *junk)
 	kvm_arch_hardware_disable(NULL);
 }
 
+static void hardware_disable_all(void)
+{
+	if (!kvm_usage_count)
+		return;
+
+	spin_lock(&kvm_usage_lock);
+	kvm_usage_count--;
+	if (!kvm_usage_count)
+		on_each_cpu(hardware_disable, NULL, 1);
+	spin_unlock(&kvm_usage_lock);
+}
+
 static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
 			   void *v)
 {
@@ -2058,7 +2109,6 @@ int kvm_init(void *opaque, unsigned int
 			goto out_free_1;
 	}
 
-	kvm_on_each_cpu(hardware_enable, NULL, 1);
 	r = register_cpu_notifier(&kvm_cpu_notifier);
 	if (r)
 		goto out_free_2;
@@ -2104,7 +2154,6 @@ out_free_3:
 	unregister_reboot_notifier(&kvm_reboot_notifier);
 	unregister_cpu_notifier(&kvm_cpu_notifier);
 out_free_2:
-	kvm_on_each_cpu(hardware_disable, NULL, 1);
 out_free_1:
 	kvm_arch_hardware_unsetup();
 out_free_0: